1. Field of the Invention
This invention relates to a medical device. More particularly, it relates to a medical device for insertion into a body, which medical device is plunged into the body tissue with only slight resistance.
2. Description of the Prior Art
Various medical devices including medical devices such as catheters which are inserted into a respiratory tract, a windpipe, a digestive tract, an urethra, a blood vessel, other body cavity, and body tissues and medical devices such as guide wires and stylets which are passed through the catheters and plunged into the body tissues are required to possess smoothness enough to attain insertion infallibly to the region aimed at without inflicting any damage on the tissues. Further, they are required to manifest ideal lubricity enough to avoid inflicting damage on mucous membranes due to friction during their retention in the tissues and consequently inducing inflammation of the affected part.
To satisfy these requirements, a method for treating the surface of a substrate of a medical device for insertion into the body with a hydrophilic polymer adapted to form an unreacted isocyanate group intended to be joined by a covalent bond to the surface of the substrate (JP-A-59-81,341), a medical device so constructed that the reactive functional group present at least on the surface of the substrate of the medical device is caused to form a covalent bond with such a water-soluble polymer as a cellulosic polymeric substance, polyethylene oxide, or water-soluble polyamide or a derivative of the water-soluble polymer and consequently the surface, on being wetted, is allowed to assume lubricity (JP-A-1-195,863), and a medical device which is so constructed that the reactive functional group present at least on the surface of the substrate of the medical device is caused to form a covalent bond with a maleic anhydride containing polymer and consequently the surface, on being wetted, is allowed to assume lubricity (JP-B-1-33,181) have been proposed.
When the entire surface of the substrate is coated with a hydrophilic polymer, however, the part of the medical device inserted in the body offers decreased frictional resistance and, at the same time, the basal part of the medical device reamining outside the body and serving as a manipulating part offers similarly decreased frictional resistance and manifests high slipperiness and degraded manipulatableness. Thus, the medical device using this coating necessitates use of a special adapter designed to facilitate the manipulation thereof.
The substrate of the medical device of this kind by its nature is required to have a flat smooth surface for the sake of improvemement in antithrombosis. The basal manipulating part of the medical device left outside the body, on being wetted with moisture such as blood, is deprived of the frictional resistance by the moisture possibly to a point where slipperiness is aggravated and manipulatableness is degraded.
For the purpose of overcoming this inferior manipulatableness, it suffices to have only the necessary part of such medical device as a catheter or a guide wire for a catheter coated with a hydrophilic and wettable resin. An attempt at partially forming the coating as by dipping, however, entails a sacrifice of the uniformity of the produced coating.
An object of this invention, therefore, is to provide a novel medical device.
Another object of this invention is to provide a medical device for insertion in the body, which medical device encounters decreased resistance to the slide thereof during the insertion in the body and enjoys improved manipulatableness while suffering no sacrifice of slidableness.